Reduction of metal by rolling mills



193 3. A. PATERSGN 3. 78%? REDUCTION O5 METAL BY ROLLING MILLS Filed 00 's. 27, 1928 AL 191 an VIZ QT 5436 92 QM M W J Patented Dec. 30, 1930 UNITED STATES PATENT OFFICE ALEXANDER EATER/SON, OF BUFFALO, NEW YORK REDUCTION OF METAL BY ROLLING MILLS 1 method.

In the art of rolling hot sheet metal, the ideal rolling operation is one in which successive reductions are effected upon a perfectly rectangular section ofinetal, each re: duction being uniform throughout the cross section of the metal so as to preserve the rectangular form which it had at the beginning. Due to the several factors which vary the contour of the rolls as, for example, roll exansion, deflection, etc., this ideal operation iias been found practically impossible of attainment. These factors may, however, be controlled to an extent such that the roll contour provided is either concave or conthickness whereby the metal is made to approach a flat or rectangular form as 1ts thickness is reduced.

With this in mind; it is noted that one method for reducing sheet metal which has been in general practice for many years past, is to j pass and repass a single sheet bar or other comparatively thick'section of metal between the same pair of rolls. to efiect, suc- V cessive reductions, the screws being setbetween each reduction to regulate or control the amount of reduction. The setting of the screws is such as to efiect the greatest reduction first, the magnitude of the succeeding reductions being progressively decreased. The rolls utilized in this method are ground con- 50 cave to an extent suchthat the concavity of vex. A convex roll contour is, however, un-,

crease progressively with a consequent progressive decrease in the convexity of the sheet. In this manner as the sheet becomes thinner, its convexity is reduced.

While the concavity of the rolls is theoretically taken up by their expansion, it will be readily appreciated that under actual operating conditions, the expansion will Vary somewhat and together with the rolling factors will cause the roll contour to vary, and in some instances the variation may be large enough to make the rolls convex. Of course, it will be understood that these variations actually are very small, in fact so small as to be imperceptible to the eye, and they have very little, if any, harmful effect upon a sin gle relatively thick sheet due to its thickpess and to the relatively large deflection occurring during the preliminary heavy reductions to which it is subjected. Obviously, however, the relative magnitude of these variations increase as the section becomes thinner (and less convex) with the result that their distortive efi'ect is increased. Consequently tht? ultimate extent to which the reduction of a single sheet can be carried out is limited to a point beyond which the variations become effective to distort the sheet. It follows, therefore, that the gauge of metal obtainable from :the rolling of a single sheet is limited, interalia, by the, extent of the variations in the contour of the rolls.

W'hen a reduction'bey'ondthe limit is desired, the procedure is to increase the thickness (and the convexity) of the section to be rolled by piling the sheets one upon another to form a pack. While the pack is a comparatively thick section when initially built up, it nevertheless must be rolled with the same care and in the same manner as the thinner single sheets. In other words it must be rolled with decreasing convexity;

otherwise the sheets of the pack may be rolled or ground into each other rendering their separation impossible. In this method, the reduction of the pack is accomplished in the same manner as that of the sheet bar, that is to say by repeated reducing passes through the same pair of rolls. This method of rolling is enerally known as the Welsh method.

The. elsh method has the objection, however, that it is slow and laborious, requiring both the manipulation of the section being reduced and the adjustment of the screws between each reduction. To avoid these objections another method has been proposed for the reduction of sheets beyond the limit to which a single sheet can be rolled. This method, for convenience, will be referred to as the continuous method.

Accordjn to the continuous method, the sheets are piled, as before, to form a fpack of convex cross section which is then ed successively through the passes provided by several separatestands, all of which function to reduce the pack. The number and design of the stands is such as will produce the esired final thickness with little or no convexity.

In the Welsh method it will be noted that the section being reduced is subjected to the same roll conditions throughout the entire process whereas in the continuous method the section is subjected to a new roll condition in each pass. In other words, each roll has a contour peculiar toitself and where successive reductions are performed in the same pair of rolls the section being reduced is, during the first reduction, fitted to such contour for all succeeding reductions and consequently no new-variations are introduced by the rolls in the succeeding reductions, but where different pairs of rolls are tilized for succ'eeding reductions, new variations ,in roll contour will be presented by each roll (and therefore in each pass) regardless of the care and skill employed to avoid it. As pointed out, the variations in roll contour determine, to a large extent, the degree to which a sheet may be reduced without distortion anditis found both by reason and experience. that the Welsh method,-.under equivalent rolling operations, will roduce a thinner sheet without distortion t an can be obtained by the continuous method. Q

It may be noted at. this time, that the sheets produced by either method are, ordinarily,

subjected to a further rolling operationlnwhich they are. assed and repassed between two rolls -for t e purpose ,of giving them some degree of finish and" flattening outwhat- V ever convexity they. may have. These rolls do not, however, operate to reduce the sheets in the sense that such term isherein used.

The principal objects of the present invention are: to obtain less variation in the roll contour provided by separate passes which are intended for the successive reduction of hot sheetmetal and to reduce the number of rolls ordinarily provided for such reduction and thereby conserve floor space.

Further objects are to obtain successive reductions of hot sheet metal in a single stand with less labor than heretofore possible and without the need of screw adjustment between successive, reductions.

By the present invention, I propose to effect at least two successive :reductions in separate ,passes which are provided by multipass, mill such as the so-called three high mill. Such procedure has the advantage of permittin successive reductions to be had without t e adjustment of screws while at the same time reducing the variations in roll contour ordinarily resulting from the provision of separate reducing passes. A reduction in roll contour variation is obtained inasmuch as the contour of one of the rolls is presented to the metal being reduced, in

both passes. whereas in the continuous method, two. new roll contours arepresented in each pass. As a result, I am able to obtain a thinner gauge product than can be obtained by the continuous method under equivalent rolling operations and with less liability of distortion.

The invention is illustrated in the accompanying drawings wherein:

Figure 1 is a top plan View of one sche-. matic, arrangement in which the invention is utilized for reducing a sheet bar to finish gauge.

Figure 2- is a side elevation of the same.

Figure 3 is a front elevation of a three high mill:v which may be utilized in the practice of the invention.

Figure 4 is a front elevation of a modified form of three high mill.

While the invention is particularly adapted for the reduction of the thinner sheets and of packs -composed of two or more sheets, it may, however, be utilized for the prelimi' nary reduction of sheet bars or equivalent sections. Furthermore, the invention may be utilized to eflect either the entire range of operation from sheet bar to finish gauge of any portion of the range, taking in, of course, at least two successive reductions. Considered in its simplest aspect, therefore, the invention consists in passing a section of metal successively through at least two passes of a multi-pass stand to effect successive reductions, the convexity of the passes being so controlled during each reduction as to effect a progressive decrease in the convexity of the section being reduced.

- One advantageous arrangement for effecting successive reductions of metal, from the sheet b'ar stage to finish gauge, in accordance with my invention "is illustrated in Figures 1 and 2. The arrangement shown includes a pair of three high stands 10 and 11 and a two high stand 12 all of which are separated by suitable heating furnaces F. A simple and effective practice contemplated in connection with the arrangement shown consists in passing a sheet bar successively through the passes provided by the first three high stand 10 and then similarly operating upon a second sheet bar, the successive operations .of the passes of the stand 10 being suificiently indicated by the arrow A. The two sections are then piled, one on the other, to form a pack which also issuccessively reduced in the passes of the first stand 10. Thus far, six reducing operations have been eflt'ected upon the same stand without necessitating any screw adjustment whatever. The pack is now passed successively through the passes of the second three high stand 11 as shown by the arrow B and, if further reduction is desired, it may be doubled or combined with another pack and again passed through the stand 11 to obtain the, final gauge. The sheets preferably are now passed to the two high stand 12, as shown by the arrow C, and thereby finished in accord ance with the usual practice. It will, of course, be understood that the sheets of the pack are separated, when necessary, during the practice of the method above outlined and that the metal is heated in the furnaces F as required.

In connection with the above practice, it 1s noted that the contour of the second pass of each stand varies from that of the first pass in such stand only insofar as the contour of one outside roll varies from the contour of the other outside roll inasmuch as the middle roll provides one-half of the contour of each pass. In this manner, the error or variation is limited to one roll. Full advantage of the relation between the passes on each stand is preferably taken during the reduction of a pack or any of the thinner sections of metal, by maintaining one side of the metal in contact with the middle roll during both reductions.

It will, furthermore, be understood that the convexity of the section is altered in each pass. The particular manner in which the convexity is controlled is'of no great moment and it may, therefore, be controlled in any suitable manner. For example, I may utilize the spring or deflection of the rolls in the the middle roll, defines a pass which will be under operating conditions, more convex than the one provided by the roll of greater stiff ness and the middle roll.

In Figure 3, a three-high stand suitable for use in the practice of the invention, is illustrated. The stand shown includes a lower roll 13, middle roll 14 and an upper roll 15. The depth of the first pass is determined by collars 16 combined with the lower roll 13 while the depth of the upper pass maybe adjusted as desired by screws 17. The use of the screws 17 has the advantage of permitting additional rolling operations on a sheet or pack when so desired. Of course, when a mill of this type is utilized in the-arrangement shown in Figures 1 and 2, for practicing the method explained in connection therewith, the screws would be given an initial or standard setting which would not, thereafter, be disturbed. 1

The drive of the rolls can be accomplished in any suitable manner. In the practice of my invention, I preferably drive the middle roll positively permitting the outside rolls to run by friction.

The passes provided by the stands 11 and 12 in Figures 1 and 2 may all he fixed or standardized by the use of stands such as shown in Figure 4. In this stand, the lower and upper rolls 13a and 15a respectively are provided with collars 16a which determine the spacing of the two passes in the stand. Of course, the collar arrangement shown is only illustrative of one of the many ways in which a fixed pass or series of passes can be obtained.

Having fully described my invention, I claim:

1. A method of reducing a section of hot sheet metal having a convex cross section consisting in passing it through at least two adj acent' passes of a multi-pass mill to effect successive reductions and controlling the convexity of the passes to reduce the convexity of the section progressively.

2. A method of reducing a section of hot sheet metal having a convex cross section consisting in passing it through at'least two adjacent fixed passes of a multi-pass mill to effect successive-reductions and controlling the convexity of the passes to reduce the con-- vexity of the section progressively.

3. A method of reducing a section of hot sheet metal having a convex cross section consisting in passing it through at least two separate passes of a multi-pass mill to effect suc- SZGSSIVG reductionsand controlling the convexity of the passes to reduce the convexity of the section progressively, one face of the sec tion reduced being placed in contact with the same roll during each reduction.

4. In the production of hot 'sheet metal, a method of effecting successive reduction consisting in passing a hot section of metal through at least two adjacent passes of a multi-pass mill to efiect successive reductions and controlling the convexity of the passes to reduce the convexity of the section progressively, similarly operating on another section, piling the reduced sections to form a pack and reducing the pack in the same manner.

5. In the production of hot sheet metal, a method of effecting successive reduction consisting in passing a hot section of metal through at least two adjacent passes of a. multi-pass mill to efiect successive reductions and controlling the convexity of the passes to reduce the convexity of the section progressively, similarly operating on another section, piling thereduced sections to form a pack, and reducing the pack in the same manner, one side of the pack being placed in contact with the same roll duringeach reduction.

6. A multi-pass mill for reducing hot sheet metal comprising a housing, a plurality of rolls arranged on said housing to provide under operating conditions at least two passes of difi'erent convexity which are adapted to etl'ect successive reductions of the sheet metal, one of the rolls being common to both passes.

7 A multi-pass mill for reducing hot sheet metal comprising a housing, a middle roll and two outer rolls supported by said housing, said rolls being arranged to provide under operating conditions two passes of different convexity which are adapted to efiect successive reductions of the sheet metal.

8. A multi-pass mill for reducing hot sheet metal comprising a housing, a plurality of rolls arranged on said housing to provide under operating conditions at least two passes of different convexity which are adaptedto efiect successive reductions of the sheetmetal, and means to standardize the depth of at least one pass, one of the rolls being common to both passes.

9. A multi-pass mill for reducing hot sheet metal comprising a housing, a middle roll and two outer rolls supported by said housing, said rolls being arranged to provide under operating conditions two passes of difierent convexity which are adapted to effect successive reductions of the sheet metal, and means to standardize the depth of the pass of greatest operating convexity.

10. A multi-pass mill for reducing hot sheet metal comprising a housing, a middle roll and two outer rolls supported by said housing, said rolls being arranged to provide under operating conditions two passes of different convexity which are adapted to eil'ect successive reductions of the sheet metal, collars arranged on the outer roll which forms a part of the pass of greatest convexity to fix the depth of such pass and adjusting screws controlling the depth of the other pass.

11. A multi-pass mill for reducing hot sheet metal comprising a housing, a middle and two outer rolls supported by said houssignature.

ALEXANDER PATERSON. 

